I'm planning a migration on a server from ColdFusion MX7 to ColdFusion 9. Does anyone know which steps I should take in order to achieve this without major issues? I can't find anything on the web that talks about this and I don't want to jump into this task without knowing what I'm up against.

Any suggestions, link to articles, etc. would be very much appreciated.

The Code Compatibility Analyzer reviews the CFML pages that you specify and informs you of any potential compatibility issues. It detects unsupported and deprecated CFML features, and outlines the required implementation changes that ensure a smooth migration.

If the Analyzer doesn't find any issues, I would then encourage you to install the developer edition and run your unit tests. (You have unit tests, right?)

If you don't have unit tests, your only other option is just to test everything manually. Good luck!

One final approach is to read the release notes for versions 8 and 9, as well as the 8.1 and 9.1 point-releases. Adobe and Macromedia were meticulous about documenting precisely what changed, which should prove helpful for you. The release notes are available as PDF for both versions 8 and 9 from Adobe.

I just did this last year when I moved code from CF 7 servers to CF 9. No issues at all with the settings or with the code. The Code Analyzer is nice, though I've never had it ding any errors with the code I'm migrating. We have many environments here (dev, test, qa, prod) so I had lots of time to get good at making sure everything was in place on the new servers before cut-over happened. So, as Adam said, test everything multiple times and assuming you don't find issues you'll probably do well.
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MilnerApr 13 '12 at 17:45

We've just recently completed the exact same upgrade, going from CF 7 to CF 9. We didn't encounter any major issues even with old application dating back to CF 5.

As Adam pointed out the Code Compatibility Analyzer is great to find potential issues such as new signatures for existing functions or scoping problem with the new local scope.

You don't want any errors as those as sure to break with CF 9, after fixing the errors you should be left with a bunch of warnings, check them to make sure it will still do what you intended. You should not ignore them and make sure you understand the implication of ignoring one.

Before starting, the most important step of all would be to backup everything. You'll want a quick way to go back to CF 7 if you ever need to so you should have a copy of the unmodified code, configurations and CFusionMX/jRun directory. I just ended up ghosting the machine in case.